The invention relates to a remote control device, by which the driver is able to perform gear change faultlessly at the synchronized mechanical transmission, having the illusion of the manual actuation of the traditional gear change lever.
It is a well known fact that in certain motor vehicles, in particular at motor vehicles with rear-drive engine, the transmission is remote from the driver. Accordingly, the gear changing element of the transmission cannot be actuated directly manually. Smaller distances may be bridged with a rod mechanism or a bowden. However, for motor vehicles or machines with an articulated design, where the driver is sitting on one of the articulated members, while the transmission is arranged on the other one, these solutions cannot be applied.
For solving the aforementioned problem, hydraulic and pneumatic systems have been developed. The essential feature of the hydraulic systems is that the driver, by means of a gear change lever, actuates pistons arranged in cylinders lying perpendicularly to each. The hydraulic liquid thus displaced actuates the pistons of remotely located working cylinders connected to the gear changing element of the transmission. Such solutions are described, e.g., in the DE-OS 25 10 392, DE-OS 27 00 837, DE-OS 29 35 377 as well as in the HU-PS 192 487.
Because hydraulic systems are based on direct force transmission, the driver may be forced to exert a rather considerable force owing to liquid friction.
With the solution described above, only motion and force are transferred, so the driver moves the gear change lever in the same way as if he were manipulating a traditional gear change lever.
With pneumatic systems the gear changing element of the transmission is connected to a shifting cylinder, arranged in the direction of shifting, and to a selection cylinder, arranged in the direction of selection. The switching cylinder and the selecting cylinder are connected to the pressurized air-system of the motor vehicle through valves. The driver manipulates said valves either mechanically or electrically. The only task of the driver is to press control buttons or to manipulate a controller arm, as would be done with automatic transmissions.
These systems, if they are simple, are highly inaccurate. The possibility of error on behalf of the driver is considerable. At the same time, the transmission gets damaged in a rather short time. On the other hand, better and more reliable systems are very complicated. For this reason development has shifted to systems which simulate manipulation of the traditional gear change lever to a certain extent.
An electropneumatic system is disclosed in the HU-PS 187 345. In this case a remote control unit is installed beside the driver and the driver moves the lever of the remote control according to the traditional shifting pattern. In every operative position the lever of remote control actuates an individual electric shift, and these are used for switching solenoid valves controlling the pneumatic shifting and selecting cylinders actuating the gear change element. This system does not, however, inform the driver on the process of gear change. At best, the end of the process is displayed by the signal lamp. As the operation of the pneumatic working cylinders normally is too hard, throttle valves used to be inserted before them. However, this solution is recommended only for transmissions which are connected to the motor through a hydrodynamic torque converter.
Essentially, the remote control unit disclosed in the DE-OS 31 38 827 can be applied to the same system. This arrangement contains electromagnets and sensors in a proper quantity such that each signal combination corresponds to a separate shift position of the remote control lever.
The remote shift unit disclosed in the U.S. Pat. No. 4,646,582 was developed for a similar purpose. Compared to the previously described solution, this embodiment is more safe, as a spring-loaded spherical locating device fixes the shift lever in its adjusted position. Furthermore, it is provided with a pneumatically actuated construction which keeps the remote control lever in its middle position as long as the requirements of gear change are met in the gear change element.
The remote shift, as described in the U.S. Pat. No. 4,516,669, effectively excludes the possibility of error on behalf of the driver and actuates the gear change element with increased safety. Gear change is possible in the released state of the clutch only, and the clutch can be closed only after having finished gear change in due order.
The U.S. Pat. No. 4,633,987 discloses a remote control device which is controlled exclusively pneumatically. This is active also in the released state of the clutch, and the remote shifting lever can be brought into the extreme position of the shifting path only after having finished the shifting process. This is the task of pneumatic cylinders.
A more suitable solution is specified in the U.S. Pat. No. 4, 646,870. This is an electropneumatic remote shifting unit, with which displacement of the remote shifting lever and displacement of the gear change element of the transmission are controlled by analog signal transmitters, namely potentiometers. With this embodiment, a pneumatic working cylinder hinders the displacement of the remote shifting lever into the extreme position prior to finishing the gear change.
While known remote shifting means meet several requirements, they are still not considered as complete. It is a well known fact that with synchronized transmission's gear change is performed in two stages. First of all synchronizing means are actuated and only after having finished synchronization, does the actual gear change take place. Synchronizing requires a smaller force, and gear change a higher force. These two stages are easily sensed by the driver on the traditional gear change lever, representing the most important prerequisite of smooth gear change.